DSL connections enable large bandwidth connections to be established over legacy twisted copper pair connections originally designed to carry simple voice calls only. The techniques employed to achieve this are sophisticated and ensuring that the correct settings are used in the DSL modems at either end of the connection in order to achieve an optimum balance between throughput characteristics (e.g. bandwidth, delay, jitter, etc.) and reliability characteristics (e.g. number of errors or errored seconds, number of resynchronizations, etc.) in a large access network is non-trivial.
Dynamic Line Management (DLM) systems attempt to monitor the behavior of lines and control their operation in order to improve the performance of the lines. The control is generally exerted by a central management device processing data resulting from the monitoring of the lines and based on that processing selecting a profile for use by the network side DSL modem (e.g. located in a Digital Subscriber Line Access Multiplexor (DSLAM), a Multi Services Access Node (MSAN) or other similar aggregation device) for use with that line.
The DSL modems themselves collect a large amount of data about the performance of the connection and this information can be useful to the centralized management function in deciding what profile should be selected for use by the network-side DSL modem (note the profile specifies values for particular parameters required by the DSL modem in order to set up the connection, such as a target signal to noise margin value and a level of interleave value, which parameters are discussed in greater detail below).
However, because an access network is likely to contain a large number of DSLAMs (or MSAN's etc.) they have generally been designed to operate as autonomously as possible. As such, although they will generally store some useful data about each digital subscriber line (hereinafter referred to simply as a “line”) to which it is connected such as the theoretical maximum rate at which the line could have been connected last time an ADSL connection was set up over the line, each DSLAM traditionally operates according to a server client model where each DSLAM operates as a server and only reacts to requests issued to it from a client. Thus in order to obtain some of the useful information stored on the DSLAM's it has been necessary generally to request the desired information and so the traditional model was to request this information periodically. This resulted in time critical information not being found out about and acted upon as quickly as might otherwise have been the case.
WO 2007/012867 describes an improvement to this situation in which DSLAM's operate proactively to transmit certain time critical pieces of information about a DSL as soon as it has synchronized in order for such time critical data to be notified to a management device as soon as possible so that, if necessary, appropriate action may be taken as soon as possible.
EP 1 995 942 A describes a DLM system in which DSL parameters are taken in respect of each DSL with a frequency which depends upon the stability of the line, such that parameters are taken in respect of stable lines only fairly infrequently whereas parameters from fairly unstable lines are taken with a relatively high frequency such that problems occurring on unstable lines may be detected and acted upon relatively quickly without wasting huge resources collecting parameters in respect of stable lines on a relatively frequent basis.
U.S. Pat. No. 5,889,470 A describes a DSL access device Management Information Base (MIB) which allows the remote management of a DSL access device by using a constructed enterprise DSL MIB to define a plurality of objects that describe the operation of a DSL access device. These objects are used to monitor the performance of, and if desired, send commands to the DSL access device.
However, each DSLAM/MSAN, etc. actually stores a large amount of useful data such as the bit loading per sub-carrier as well as the Signal to Noise Ratio (SNR) per sub-carrier which is also available as soon as the connection has been established and it would be desirable to provide an efficient mechanism for providing this data to a central processing station where the data can be processed.